1. Field of the Invention
The present invention relates to an epoxy resin composition for encapsulating a semiconductor, and more particularly to an epoxy resin composition containing a phenol-modified silicon-containing compound used for such a purpose.
2. Related Art Statement
In recent years, semiconductors are predominantly encapsulated with resins, and epoxy resin compositions are commonly used for such purpose in consideration of excellent adhesiveness and relatively low cost of the epoxy resin compositions. However, further technical improvements are required for maintenance of the encapsulated semiconductor. One of the important tasks is the improvement of reliability against humidity and another important task is the reduction in internal stress caused by shrinkage upon curing and by differnce in thermal expansion coefficients of the resin and the semiconductor elements.
Particularly for the encapsulation of a large integrated circuit including a large size elements, cracking of the resin due to internal stress or stress caused by thermal shock poses a serious problem.
In order to solve such a problem, various investigations have been made with the aim at reducing the internal stress of the resin by decreasing the thermal coefficient of the resin composition to bring the same closer to the thermal expansion coefficient of the elements of the integrated circuit or by lowering the modulus of elasticity of the resin composition.
In general, the thermal expansion coefficient may be decreased by adding an inorganic filler having a small thermal expansion coefficient in the resin composition. However, since the modulus of elasticity is increased by the addition of an inorganic filler, the reduction of the internal stress is not sufficient. Moreover, if a large amount of an inorganic filler is added to the resin composition, problems arise due to poor moldability and low fluidity. The modulus of elasticity is lowered by the addition of an elastic additive to the resin composition. The elastic additives used for this purpose are rubbers (as disclosed by Japanese Patent Laid-Open Publication No. 131223/1982) and elastic silicone compounds. Silicone compounds are expected to be well suited for such purpose since they are superior over conventional rubbers in resistance to heat and contain only little impurities. Conventional techniques for the inclusion of silicone compounds include the addition of a silicone compound which is not reactable with the resin as disclosed by Japanese Patent Laid-Open Publication No. 219218/1983, and the addition of a silicone compound having a functional group reactable with the resin as taught by Japanese Patent Laid-Open Publication Nos. 145942/1981 and 138730/1983. However, the internal stress of the resin composition could not be lowered to a satisfactory level by the techniques taught by the preceding trials. A silicone compound which is not reactable with the epoxy resin compound is only weakly bound with the epoxy resin at the interfaces therebetween, and such a silicone compound and the epoxy resin are poor in mutual miscibility so that the silicone compound is not dispersed homogeneously in the resin, leading to unsatisfactory results. On the other hand, a silicone compound having a functional group reactable with the epoxy resin is also poor in mutual miscibility with the resin, leading to unsatisfactory reduction in internal stress of the final resin composition.